Decide whether want to find out all-time or current record sales since the information is revised every week. For all-time sales, visit RIAA.com and check the "Gold & Platinum" section. From there, you have several choices, depending on whether or not you are researching albums, artists or certifications. For current record sales, visit Billboard.com or subscribe to the magazine. Many public libraries carry Billboard due to its historic and authoritative credibility for over one hundred years. Billboard, however, does not list the number of units sold except in certain news stories or in sister publications meant for industry use.
Read the news section of Billboard and other music trade publications. Billboard sometimes lists units sold on a record's first week sales, which can be a newsworthy event if the sales hit an industry milestone. In many cases, first week sales mark the peak of popularity for that product, as in the case of the movie industry. Billboard lists the latest RIAA certifications for Gold, Platinum and Multi-Platinum awards.
Go to Billboard.biz and find the section called "Ask Billboard." Email a question. Billboard keeps an archive of all of its historical chart information that dates back to the 1890s. Billboard sells its historical chart information via its website as well as its publications compiled by Joel Whitburn, whose website is RecordResearch.com.
Contact someone in the music industry or a journalist who publishes Nieslsen Soundscan information in their writing. It is very difficult to get access to this information if you do not work in the radio or music industries, or you do not subscribe to the service. However, Nieslen Soundscan is the most comprehensive and complete resource for current record sales. Researching musical products that sold less than a half million units is much more difficult to determine. For all-time sales, it is near impossible to get an estimate without going directly to artist management.
Visit the website of the artist you are researching. Some artist websites list sales data if sales have been substantial, but most artists tend to avoid presenting the commercial side of their careers in order to keep fans focused on the artistic side. Nevertheless, almost every artist has a management company that tracks sales information. Look for management contact information and let them know why you need the information and there is a chance they can provide it for you, or at least direct you to another source. If you cannot find management contacts on the artist website, artist management directories are published by Billboard.